U.S. patent number 5,669,524 [Application Number 08/273,355] was granted by the patent office on 1997-09-23 for enclosures.
This patent grant is currently assigned to Chem-Tronics, Inc.. Invention is credited to Chris W. Loedel.
United States Patent |
5,669,524 |
Loedel |
September 23, 1997 |
Enclosures
Abstract
Lightweight, structurally integral enclosures with walls
stiffened and strengthened by integral and joined reinforcing ribs
which may also serve as heat sinks. These ribs, which may be capped
or uncapped and located on the inner or outer sides of the
enclosure walls, are formed by chemical milling. Wall components
are preferably joined by electron beam welding. Seals may be used
between the walls and a closure to isolate the interior of the
enclosure. In electronic applications, conductive seals and
sealants are employed to provide uniform and continuous shielding
from electromagnetic interference and radio frequency
interference.
Inventors: |
Loedel; Chris W. (San Diego,
CA) |
Assignee: |
Chem-Tronics, Inc. (Cajon,
CA)
|
Family
ID: |
23043566 |
Appl.
No.: |
08/273,355 |
Filed: |
July 11, 1994 |
Current U.S.
Class: |
220/9.1;
220/669 |
Current CPC
Class: |
H05K
7/1424 (20130101); H05K 9/0062 (20130101) |
Current International
Class: |
H05K
9/00 (20060101); H05K 7/14 (20060101); B65D
025/14 () |
Field of
Search: |
;220/9.1-9.3,669,414,401,493 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Moy; Joseph M.
Attorney, Agent or Firm: Hughes, Multer & Schacht,
P.S.
Claims
What is claimed is:
1. A lightweight, structurally integral housing which has walls
bounding a defined space, said wails being fabricated entirely of a
metallic material and each of said walls being a chemically milled
component which has a skin and an array of integral reinforcing
ribs on one side of said skin, said ribs being fabricated from the
same material as said skin.
2. An enclosure as defined in claim 1 in which the ribs in the
array are arranged in a rectangular pattern.
3. An enclosure as defined in claim 1 in which the ribs in the
array are arranged in a triangular pattern.
4. An enclosure as defined in claim 1 in which the ribs are located
on outer surfaces of said walls.
5. An enclosure as defined in claim 1 in which the ribs are located
on inner surfaces of said walls.
6. An enclosure as defined in claim 1 in which said walls have
separate arrays of primary ribs and secondary ribs, said primary
ribs and said secondary ribs having different cross-sectional
configurations.
7. An enclosure as defined in claim 1 or claim 6 in which said
walls have ribs with an uncapped cross-sectional configuration.
8. An enclosure as defined in claim 1 in which said walls have ribs
with a capped cross-sectional configuration.
9. An enclosure as defined in claim 1 in which the metallic
material is titanium aluminide; a titanium alloy; or aluminum,
nickel niobium, beryllium, or copper or an alloy thereof.
10. An enclosure as defined in claim 1 in which the metallic
material is reinforced with particles of graphite, silicon carbide,
silicon nitride, glass fiber, silica, or boron nitride.
Description
TECHNICAL FIELD OF THE INVENTION
The present invention relates to enclosures (or containers) and,
more particularly, to novel, improved, strong and lightweight
containers which are particularly suited for demanding
applications; e.g., to shield electronic components from EMI
(electromagnetic interference) and RFI (radio frequency
interference) and in marine and other environments in which
pressure and corrosion resistance are required.
BACKGROUND OF THE INVENTION
The transportation of electronics equipment on air, land, and sea
requires safe containment or packaging. Particularly for avionic
applications, the cabinet housing the electronics needs to be tough
and vibration resistant, yet lightweight because, increasingly,
electronics have become significant negative weight contributors to
the flying platform. Similarly, ground transported electronic and
hand-held test equipment need to be lightweight to lessen fuel
consumption and ease manual carry. There is also a requirement that
any reduction in weight be so done that the enclosure still meet
the rigorous vibration, shock, thermal dissipation, and
environmental condition requirements (EMI, RFI, moisture, salt)
established by the military and by commercial transport
agencies.
Current efforts to reduce enclosure weight have concentrated on the
use of lightweight composites or plastics although enclosures with
machined metallic wall components have also been proposed. While
enclosures made from those materials may weigh less than
conventional enclosures, they have several major drawbacks; the
first is price. In a program conducted by the Navy, a composite 3/4
A.T.R. (air transport rack) enclosure was costed at $1,000 to
$1,800 per manufactured pound. For a composite box weighing 6.7
pounds, this equates to a price of $6,700.
A second drawback of non-metallic enclosures designed for the
demanding applications under discussion is that they are natural
insulators. Epoxy metal particulates or wire mesh integration is
required to dissipate heat and/or to shield packaged components
from EMI and RFI These requirements add to the complexity of
design, unit weight, and manufacturing complexity and thus cost.
Another drawback is that non-metallic or plastic enclosures can
degrade in ultraviolet and visible light.
SUMMARY OF THE INVENTION
There have now been invented, and disclosed herein, certain new and
novel enclosures which are designed for the demanding applications
discussed above and others of that character but are free of the
drawbacks of the enclosures heretofore available or proposed for
such applications.
The walls of these novel enclosures are fabricated from metallic
materials chemically milled to a configuration which yields
significant structural weight savings and, at the same time,
vibration, shock, and corrosion resistance. This configuration
consists of a thin skin with an array of integral stiffening and
reinforcing ribs. The ribs may be on either the outside or the
inside of the enclosure walls, and they may be arranged in a
triangular or rectangular pattern. The ribs may be capped (i.e.,
have a "T" or "hourglass" section) or uncapped. Complementary
arrays of capped and uncapped ribs may also be employed. In
addition to their stiffening and reinforcing properties the
integral ribs have the advantage that they are effective heat sinks
and thus capable of dissipating significant amounts of thermal
energy, a particularly important advantage in applications in which
electronic or other heat sensitive components are packaged in the
enclosure.
Other advantages of the resulting structures are superiority in
their ability to dissipate thermal energy and to provide EMI and
RFI shielding.
Other benefits of the novel enclosures disclosed herein include the
following:
1. Easily integrated through holes, attachment points for handles,
latches, door hinges, and internal mountings.
2. A low cost/weight ratio of fabrication, yielding enclosures
typically costing 25 percent less than enclosures of the same
weight manufactured from the advanced composites investigated by
the Navy.
3. Versatility in that they can be produced from various metallic
materials including titanium aluminide; titanium alloys; and
aluminum, nickel, niobium, beryllium, and copper and their
alloys.
Still other advantages of the present invention, attributable to
the use of chemical milling as the manufacturing process of choice
include:
1. Weight reduction to minimum allowable design thicknesses without
the inducing of manufacturing stresses or alteration of the
enclosure configuration.
2. The ability to impart structure after enclosure assembly in
circumstances where conventional machining would be costly and
often impossible since many of the enclosure features would be
inaccessible to cutting tools.
3. All required metal removal for an entire enclosure assembly is
accomplished in one time period.
The important advantages, features, and objects of the present
invention will be apparent to the reader from the foregoing and the
appended claims and as the ensuing detailed description and
discussion proceeds in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of one representative enclosure
constructed in accord with and embodying the principles of the
present invention and having walls chemically milled into a
lightweight configuration consisting of a thin skin with an array
of integral and joined, stiffening, reinforcing, and heat
dissipating ribs;
FIGS. 2, 3, and 4 depict three of the cross-sections which the ribs
of the FIG. 1 enclosure may have;
FIG. 4A is a fragmentary section through the cover of an enclosure
embodying the principles of the present invention;
FIG. 4B is a fragmentary section showing the FIG. 4A cover attached
to the shell of the cover with an O-ring between the cover and
shell to isolate the interior of the cover;
FIG. 5 is an exploded view of an enclosure embodying the principles
of the present invention and differing from the enclosure depicted
in FIG. 1 in that the integral ribs of its wall components are
formed on the inner surfaces of those components rather than on the
outer surfaces as they are in the FIG. 1 enclosure;
FIG. 6 is a perspective view of a complex enclosure shell with six
wall components;
FIGS. 7-12 are views looking from the inside of the shell at the
wall components of the FIG. 6 shell;
FIG. 13 is a perspective view of an enclosure wall component which
embodies the principles of the present invention and separate
arrays of stiffening, reinforcing, and heat dissipating ribs of two
different configurations;
FIG. 14 is a section through the wall component of FIG. 13, taken
essentially along line 14--14 of that figure; and
FIG. 15 is a perspective view of an enclosure wall component which
embodies the principles of the present invention and has an array
of integral and joined, reinforcing, stiffening, and heat
dissipating ribs arranged in a triangular pattern.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, FIG. 1 depicts an enclosure or
container 20 constructed in accord with, and embodying, the
principles of the present invention. Enclosure 20 has end walls,
front and back walls, a top wall, and a bottom wall. The front
wall, one end wall, and the top wall are shown in FIG. 1; and these
walls are respectively identified by reference characters 22, 24,
and 26. The two end walls, the top wall, and the bottom wall are
all integral parts of a single enclosure component or shell 28, and
the front and back walls are separate components.
All six walls of enclosure 20 (the illustrated front, right-hand
end, and top walls 22, 24, and 26 and the hidden left-hand end,
bottom, and rear walls) are of the same novel construction. Each
has a thin skin 30 reinforced and stiffened by a rectangular array
32 of integral, external, joined, reinforcing and heat dissipating
ribs 34. Ribs 34 may have an uncapped configuration. A rib of that
character is depicted in FIG. 2 and identified by reference
character 34-2. Alternatively, the ribs may be capped.
Representative rib configurations of that character are illustrated
in FIGS. 3 and 4 and identified by reference characters 34-3 and
34-4, respectively.
Typically, rib 34-2 will have fillets 36 with a radius equaling
TP-TS where TS is the thickness of skin 30 and TP is the distance
from the top 38 of rib 34-2 to the furtherest surface 40 of the
wall in which the rib is integrated.
The rib 34-3 depicted in FIG. 3 has an hourglass cross-sectional
configuration and fillets 42. Like the corresponding fillets of
ribs 34-2, those identified by reference character 42 will
typically have a radius of TP-TS/2 where TP and TS have the
meanings assigned above and the top the integral rib 34-3 is
identified by reference character 44. Rib 34-3 also has a cap 46
with concave sides 48. Cap 46 extends from the outermost ends of
fillets 42 to the top 44 of rib 34-3.
The capped rib 34-4 depicted in FIG. 4 has a T-shaped cross-section
defined by a web 50 and a cap or flange 52 which extends from the
upper ends of fillets 53 to the top 54 of the rib. In this case,
the fillet radius will typically be one-half the difference between
the width W of cap 52 and the width WW of web 50.
Wall structures with a thin skin and reinforcing, stiffening, and
heat dissipating ribs of the character depicted in FIGS. 2 and 4
and identified by reference characters 34-2 and 34-4 can be made
with one chemical milling stage. Generation of the T-like
configuration shown in FIG. 3 requires two chemical milling
stages.
Representative metallic materials from which enclosure 20 can be
made are identified above. The metallic material can be loaded with
a particulate reinforcement for increased strength if desired.
Suitable reinforcement materials include: graphite, silicon
carbide, silicon nitride, glass fiber, silica, and boron
nitride.
The three components of container or enclosure 20--the back wall,
the front wall 22, and the shell 28--are similar with the
construction of shell 28 being typical. Consequently, only the
fabrication of that component will be described in detail
herein.
The first step in constructing shell 28 with a FIG. 2 or FIG. 3 rib
configuration is to form a blank of the selected sheet stock into
the configuration illustrated in FIG. 1. Next, the blank is cleaned
and otherwise prepared for chemical milling. The blank is then
masked; and the maskant is scribed and removed, exposing those
areas of the blank where metal is to be removed. The shell is then
immersed in a batch of etching solution to remove the unwanted
metal.
At the end of the etching step, shell 28 is withdrawn from the
etching solution; and the mask is stripped away. The shell is then
benched (deburred) to remove sharp edges produced by the chemical
milling process, and the manufacturing process is completed by
final trim machining and the assembly of details (if any) to the
shell. Representative operations for final detail assembly include:
drilling and tapping for inserts; drilling of through holes for
rivets; installation of O-rings; application of conductive EMI and
RFI sealants; and the attaching of handles, latches, gauges, and
shock prevention and safety equipment.
If a FIG. 3 or comparable rib configuration is selected, a second
chemical milling stage follows the removal of the shell from the
first stage etching solution. The shell is typically washed to
remove any remaining vestiges of the etching solution and remasked.
The masking material is then stripped away from those areas which
will become the fillets 42 of ribs 34-3. After the maskant is thus
selectively stripped away, shell 28 is again immersed in an etching
solution to remove metal from the unmasked areas. At the end of
this step, the shell 28 is removed from the etching solution and
the mask stripped away. The second chemical milling stage is
followed by steps such as those discussed above--e.g., benching,
trim machining, and the assembly of details.
Typically, the rear or back wall of container 20 will be
permanently integrated with shell 28. Brazing, adhesive bonding,
and mechanical fasteners (bolts, rivets, pins, etc.) may be
employed for this purpose. However, electron beam welding is
preferred because of its speed, low input of heat to the parts
being joined, and quality of the bond.
The front wall or cover 22 of container 20 will typically be
assembled to shell 28 with mechanical fasteners so that it can be
removed for the installation and removal of electronic or other
components. Only attachment features and covers require special
negation of thermal energy buildup, RFI, and EMI. In the case of
the cover, these issues can typically be dealt with in the same
manner described above as they are in the case of the other
enclosure components.
As shown in FIG. 4B, a seal 56 such as an O-ring may be installed
between cover 22 and shell 28 to isolate the interior 58 of
enclosure 20. This keeps foreign matter from reaching the interior
of the enclosure and, if present, keeps inert or other protective
gases from escaping through the joint 60 between cover 22 and shell
28. A conductive O-ring may be employed if EMI or RFI shielding are
required.
O-ring 56 is seated in a groove or recess 62 which opens onto the
inner side 64 of cover 22 and in a complementary recess 66 which
opens onto the cover-facing edge 68 of shell 28.
Referring still to the drawings, FIG. 5 depicts an enclosure or
container 120 which has a shell 122 with a top wall 124, a bottom
wall 126, and end walls 128 and 130. The enclosure also has
removable front and back walls (or covers) 132 and 134.
In addition to having two removable covers, container 120 differs
significantly from the enclosure 20 depicted in FIG. 1 in that the
integral ribs employed to stiffen and strengthen shell 122 and
covers 132 and 134 and to dissipate heat are internal instead of
external.
The construction of each enclosure component is similar. Each
component has one (or more) rectangular arrays 138 of integral,
joined, stiffening, strengthening, and heat dissipating ribs 140; a
thin skin 142; and a marginal portion 144 typically equal in
thickness to the plate stock from which the components are
fabricated. The ribs may be capped or uncapped and of any
appropriate configuration; e.g., one of those shown in FIGS.
2-4.
In addition to illustrating an enclosure with an internal rib
system, FIG. 5 shows that components of considerable complexity
such as the illustrated enclosure shell 122 can be fabricated by
the novel techniques disclosed herein; and, as suggested above,
this can be easily and inexpensively done.
FIGS. 6-10 depict an even more complicated enclosure shell 220 with
six wall components 222 . . . 232 all of complex configuration and
all expeditiously and inexpensively fabricated by the novel
manufacturing technique disclosed herein. Each of the six wall
components 222 . . . 232 has an internal array of integral, joined,
stiffening, reinforcing, and heat dissipating ribs. The wall
components may be assembled by electron beam welding.
The rib arrays employed in components 222, 224, 228, and 232 are of
the rectangular character discussed above and shown in FIGS. 1 and
5. Those arrays are identified by reference characters 234 . . .
240 with the lower rib 234L . . . 240L in each of these arrays
having a stepped or picket fence configuration.
Enclosure components 226 and 230 have ribs which follow contours of
these wall components. These ribs are identified by reference
characters 242 . . . 248 in FIG. 9 and by reference characters 250
. . . 254 in FIG. 11.
The ribs of the six wall components 222 . . . 232 may have any
appropriate cross-sectional configuration such as one of those
depicted in FIGS. 2-4.
FIGS. 6-12 demonstrate even further the application of the
principles of the present invention to the construction of
containers and enclosures of great complexity.
It was pointed above that one can sometimes employ to advantage in
container wall components embodying the principles of the present
invention and employing a combination of capped and uncapped,
stiffening, reinforcing, and heat dissipating ribs. A wall
component of that character is depicted in FIGS. 13 and 14 and
identified by reference character 320.
Wall component 320 has a rectangular array 322 of joined capped
ribs 324 of the configuration shown in FIG. 14. It also has two
separate, rectangular arrays 326 and 328 of secondary, uncapped,
joined ribs 330. Those ribs have a configuration resembling that
shown in FIG. 2.
Secondary, uncapped ribs 330 suppress vibrations in wall component
320 by raising the resonant frequencies of the skin 332 of that
component to levels where resonance no longer poses a problem.
Furthermore, the secondary ribs 330 significantly reduce any
tendency toward elastic buckling of the skin and otherwise make the
component more structurally stable. All this is accomplished,
moreover, with a much smaller increase in weight than would be
possible if the obvious alternative of more closely spacing capped
ribs 324 were employed. The height of the secondary ribs 330 will
typically range from one-tenth to one-half of the height of the
capped ribs 324.
The arrays 326 and 328 of secondary ribs are formed in pockets 334
and 336 bounded by ribs 324 of array 320. The secondary ribs in
each pocket extend to and join the pocket bounding primary ribs
324.
It was also pointed out above that integral ribs providing
stiffening, reinforcing, and heat dissipation can be arrayed in a
triangular pattern instead of the rectangular array employed in the
previously disclosed embodiments of the invention. A container wall
component with a triangular rib array is illustrated in FIG. 15 and
identified by reference character 420.
The array of ribs is identified by reference character 422, the
ribs making up the array (and joined at nodes 423) by reference
character 424, and the skin of wall component 420 by reference
character 426. Once again, the ribs may have any appropriate
cross-section including one of those depicted in FIGS. 2-4.
The invention may be embodied in many forms without departing from
the spirit or essential characteristics of the invention. The
present embodiments are therefore to be considered in all respects
as illustrative and not restrictive. The scope of the invention is
indicated by the appended claims rather than by the foregoing
description, and all changes which come within the meaning and
range of equivalency of the claims are therefore intended to be
embraced therein.
* * * * *